I have a guy near me who is selling 4 C&D batts UPS 12-490MR for $100 for all 4. They are slightly older he used them wired in series in a 48V Home UPS setup. Says they all hold a load and I asked him what the resting voltage is but I haven't heard back yet. Anything I should know beforehand? I want some advice if I should get them or just pass. He says they are not equal and no longer useful for series wiring. But since we don't use them in a series would it be a good buy?